Fig. not to stay in one place for a long time; to be always on the move. He is always doing something. He never lets the grass grow under his feet.I have always thought that I ought not to let the grass grow under my feet.Jane: Last night I told Alan that we needed a new bookshelf, and he had built one by the time I got home today. Jill: Boy, he doesn't let the grass grow under his feet.